Conventionally, microfabrication has been carried out by lithography using a photoresist composition in production of semiconductor devices. The microfabrication is a machining process in which a thin film of a photoresist composition is formed on a substrate to be processed, such as a silicon wafer, the film is irradiated with an active light such as ultraviolet light through a mask pattern in which a pattern of a semiconductor device is depicted, the pattern is developed, and the substrate to be processed, such as a silicon wafer, is etched using the obtained photoresist pattern as a protective film. In recent years, however, semiconductor devices have been further integrated, and the active light to be used has been shifted to a shorter wavelength, from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). This raises serious difficulties due to the effects of diffuse reflections of active light from a substrate and standing waves. Therefore, a method for providing an anti-reflective coating (Bottom Anti-Reflective Coating, BARC) between the photoresist and the substrate to be processed has been widely studied.
Hereafter, when formation of finer resist pattern progresses, an issue of resolution and an issue of resist pattern collapse after development arise and thus thinner resist film formation is desired. Therefore, it is difficult to obtain a sufficient resist pattern film thickness in substrate processing. As a result, a process has been required in which not only the resist pattern but also a resist underlayer film formed between the resist and the semiconductor substrate to be processed have a function as a mask at the time of the substrate processing. As a resist underlayer film for the process as described above, different from a conventional high etch rate (etching rate is fast) resist underlayer film, the following resist underlayer films have been required: a resist underlayer film for lithography having a selectivity of a dry etching rate close to that of a resist, a resist underlayer film for lithography having a selectivity of the dry etching rate smaller than that of a resist, and a resist underlayer film for lithography having a selectivity of the dry etching rate smaller than that of a semiconductor substrate.
As polymers for the resist underlayer film, for example, the following polymers are exemplified.
A resist underlayer film forming composition using polyvinyl carbazole is exemplified (refer to Patent Document 1, Patent Document 2, and Patent Document 3).
A resist underlayer film forming composition using a fluorenephenol novolac resin is disclosed (refer to Patent Document 4, etc.).
A resist underlayer film forming composition using a fluorenenaphthol novolac resin is disclosed (refer to Patent Document 5, etc.).
A resist underlayer film forming composition containing a resin in which fluorenephenol and arylalkylene are repeating units is disclosed (refer to Patent Document 6, Patent Document 7, etc.).